U.S. Pat. No. 4,594,138 to Thompson discloses a fluid filter including a plurality of perforated plate-like electrodes, interleaved with porous filter media, disposed within a housing. A pair of conductive bus bars extend along the outside of the housing, and each makes connection to alternating electrodes via a pin-and-tab arrangement. The bus bars are connected to a suitable voltage source, whereupon fluid flowing through the housing passes through the electrodes and filter media and is subjected to an electric field, directed either parallel or anti-parallel to the direction of flow. The electric field causes the suspended particles to agglomerate or flocculate so that they may be more efficiently captured by the porous filter media. In operation, particles flow over the positive electrodes and begin significant adhering at the negative electrode.
Such fluid filters have proven to be extremely effective in removing particulates from dielectric fluids such as hydraulic fluid. Fluids that would require many passes through conventional filters can be cleaned in one pass through the agglomerating filter.